Empire of Electronics

Chapter 1.5 - Ferrite Element

Thanks to the mineral detector, radar development has progressed from basic performance confirmation to the stage of substantial performance improvement. To enhance the radar's performance, improvements in the performance of the magnetron used in it are also necessary. As we contemplate future improvement measures, Lieutenant Commander Rikurō Mochizuki, who used to work in communications at the Kure Naval Arsenal but has now joined our organization due to the expansion of the radar unit, came to consult.

"It's about ferromagnetic ferrite, but it seems that materials with improved magnetic properties have recently become available. It's said that they can be manufactured by a company called Tokyo Electric Chemical Industry. How about going to see if we can use it in our equipment?"

"I've heard about the company that started producing ferrite. I believe a professor from the Tokyo Institute of Technology was conducting research on ferrite and established a company to manufacture it. If high-performance ferrite becomes readily available, it seems there could be various applications for it. Let's go visit them right away."

Magnetic materials are one of the most important materials for electronic devices. After all, electromagnetic waves themselves are waves of electric and magnetic fields. In devices that utilize electromagnetic waves, there are various components that utilize magnetism, but among them, the magnetron utilizes the resonance phenomenon of electrons generated by applying a strong magnetic field from outside the vacuum tube. For the magnetron, strong magnetism greatly affects its performance. It is also highly important as a component in motors. Furthermore, magnetic materials are necessary as materials for electronic components such as coils and transformers.

In April 1938, we promptly visited Tokyo Electric Chemical Industry in Kamata, accompanied by Engineer Nakajima, a magnetron specialist from Japan Radio Company. During the visit, Dr. Takei, one of the inventors of ferrite, personally explained to us.

"Ferrite is a material formed by oxidizing compounds of iron with zinc or nickel, which have strong magnetic properties, and sintering them at high temperatures. We were able to experimentally manufacture the first ferrite in the world as early as 1929. Well, it was my colleague Dr. Katō and I who researched and invented it. About two years ago, we established this company to mass-produce ferrite. Production of ferrite components for radio equipment is entirely feasible. Regarding the magnetic properties of ferrite, we have improved them by about 20% compared to when the company was established, through adjustments in the mixing ratio of components and refinements in the sintering process at high temperatures."

Nakajima promptly asked a question. "When using it for a magnetron, it's necessary to shape it to fit the outer shape of the vacuum tube. Is it possible to process it into various shapes like hollow circles or semicircles that match the diameter of the tube?"

"Of course, with the appropriate molding dies, it's possible to shape it into various forms. If we assume a shape resembling a ring with holes, I believe we can process it even with a diameter about half that of a 5-sen coin."

High-power magnetrons use powerful electromagnets. On the other hand, I was considering using simple magnets for the receiving side's low-power magnetron.

"I'm considering using a magnetron for local oscillation in the receiving circuit as well, for high-frequency oscillation. It seems convenient for power saving and miniaturization, doesn't it?"

Nakajima immediately agreed.

"I see, you're planning to use a magnetron for local oscillation in the receiving circuit. Indeed, it doesn't require much power, but it needs to be stable in frequency and compact. Well, even in transmitting circuits, there are plenty of uses for small-sized radios or onboard radars that don't require as elaborate setups as electromagnets."